1. Field of the Invention
The present invention relates to a secondary battery, and more particularly, the present invention relates to a lithium secondary battery.
2. Description of the Related Technology
Lithium secondary batteries mainly use lithium-based oxide as positive electrode active materials and carbon as negative electrode active materials. In general, lithium batteries are classified into liquid electrolyte batteries and polymer electrolyte batteries according to the kind of the electrolytes used therefor. The liquid electrolyte batteries are called “lithium ion batteries” and the polymer electrolyte batteries are called “lithium polymer batteries”. In addition, the lithium secondary batteries can be fabricated with various shapes, such as cylindrical lithium secondary batteries, square type lithium secondary batteries, or pouch type lithium secondary batteries.
Typically, the cylindrical lithium secondary battery includes an electrode assembly comprising a positive electrode plate coated with a positive electrode active material, a negative electrode plate coated with a negative electrode active material and a separator interposed between the positive electrode plate and the negative electrode plate for preventing short circuit while allowing the movement of lithium-ions exclusively, a cylindrical case for receiving the electrode assembly, and an electrolyte contained in the cylindrical case in order to enable lithium-ions to move.
Such a cylindrical lithium secondary battery is fabricated as follows: First, the electrode assembly is prepared by stacking the positive electrode plate, which is coated with the electrode plate, which is coated with the negative electrode active material and connected to a negative electrode tab, and a separator and then rolling or winding the positive electrode plate, the negative electrode plate and the separator into a cylindrical roll. After that, the cylindrical electrode assembly is fixed in the cylindrical case and the electrolyte is filled into the cylindrical case. Then, the cylindrical case is sealed, thereby obtaining the cylindrical lithium secondary battery.
In general, a cavity is formed at a center of the electrode assembly of the cylindrical lithium secondary battery. Such a cavity may cause the electrode assembly to be released or easily deformed. Thus, there has been a need to minimize the release or deformation of the electrode assembly.